Ac 24 V Power Line Cable Lengths - Siemens Desigo TRA Engineering, Mounting And Installation Manual

Power consumption of the triacs on DXR2 AC 24 V
Max. power consumption of DXR2 AC 24 V
Cable cross-section
2.50 mm
1.50 mm
1.00 mm
Notes
Siemens
Building Technologies
Per triac
Unconfigured triac
(Reserve for later configuration)
Thermal actuators with a starting power of 6 VA (not pre-heated):
If driven by a 5...50% PWM signal, they only count for 3 VA.
Due to internal heat dissipation, the max. power consumption of the devices is
limited (sum of base load, KNX supply, field supply, and triacs):
Device Max. power
DXR2.M11 58 VA / 2.416 A
DXR2.M12P 58 VA / 2.417 A
DXR2.E12P 60 VA / 2.5 A
DXR2.M18 70 VA / 2.917 A
DXR2.E18 72 VA / 3 A
6.3.4

AC 24 V power line cable lengths

The permissible voltage drop of 0.48 V (2%) on the power wire between the
transformer and the most distant power point (room automation station, power
supply module, bus connection module) is the basis for calculations.
The table below provides cable lengths and cable cross sections based on load.
5 VA
Power
2
/ AWG14
135 m
440 ft
2
/ AWG16
85 m
280 ft
2
/ AWG18
55 m
180 ft
The supply (AC 24 V) and return lines ( ) can each have the indicated lengths.
Each supply point (room automation stations/power supply module/bus
connection module) is either connected separately to the transformer's terminal
block (star wiring) or looped via the room automation station.
Power is added together for multiple back-to-back looped devices ("daisy chain")
which reduces the cable length accordingly.
Cables may be wired in parallel to increase the cross section.
In practice, the small level of permissible voltage drop off means that the
transformer must always be installed in close proximity to the TRA devices
and that any cascading powering of room automation stations is only
possible over short distances or at small outputs.
Desigo TRA Engineering, mounting and installation
Wiring of power lines
Max. power with cold thermal actuators
94 VA / 3.917 A
94 VA / 3.917 A
96 VA / 4 A
96 VA / 4 A
96 VA / 4 A
Cable length
10 VA 20 VA 50 VA
70 m 35 m
220 ft 110 ft
42 m 21 m
140 ft 70 ft
27 m 13 m
90 ft 45 ft
6 VA / 250 mA
6 VA / 250 mA
100 VA 200 VA
13 m 7 m
44 ft 22 ft
8 m 4 m
30 ft 15 ft
5 m 3 m
17 ft 9 ft
CM111043en_09
2016-02-22
3 m
11 ft
2 m
7 ft
1 m
4 ft
31 / 84